Antony Green is the ABC's election analyst. His expert views on the nation's 150 electorates will be heard throughout the election campaign on ABC radio and television news, current affairs programs and on election night. More »

How are the margins for each electorate and party calculated?

There are two sources for the margins used on this site. For electorates that have not been subject to a redistribution, the margin is the 2-candidate preferred margin for the winning candidate at the 2007 election. Where there has been a redistrution, a new margin has been estimated by re-allocating polling place results from the 2007 to match the new electoral boundaries.

When the electoral boundaries were released, I published estimated margins for all seats on my blog. I am no longer using these margins as I have switched to adopt the estimated margins produced by the Parliamentary Library and the Australian Electoral Commission (AEC). The AEC has information on where people live and where they votes, and so is able to estimate booth results back to census collector districts and re-aggregate the results. The same detail can be applied to re-allocating postal, absent and pre-poll votes. This is more accurate than my rough re-allocation of polling booths.

The margins for all seats can be found in this document at the AEC website. The AEC publishes all the margins to two decimal places, but I think this is unecessary except for the most marginal of seats. I use the same margins in all seats but rounded to one decimal place. Using the AEC margins means the figures will match the data fed to us on election night.

Some people prefer to round all margin up to the next decimal place. I choose not to do that on this site as this gets confusing in trying to publish results on election night if the margindoesn't match the swing you are using to give the seat away.

I need to stress that all the margins I use are estimated results of the 2007 election. They are not predictions for the 2010 or estimates based on polls. They are simply estimates of what the result of the 2007 election might have been had it been fought on the new electoral boundaries.

The results of by-elections are also ignored and all margins are based on the 2007 election.

What constitutes a marginal or safe electorate?

A marginal seat is just an issue of definition. The AEC defines all seats with a margin if under 6% as being marginal, and that's a definition also adopted on my ABC site. The AEC classifiesd seats between 6% and 10% as Safe and seats above 10% as Very Safe. I prefer to put the cut-off between Safe and Very Safe at 12% just to provide the ABC election site and results system with more seats in the Safe category.

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Will you be setting up Senate Calculators for this election?

Yes.Nominations close at noon on Thurday 19 July, with the release of names and ballot draw after noon on Friday. Names will be released to the media on Friday afternoon and I will have them all up on this website by early evening.

The Grout Ticket Votes must be lodged by noon on Saturday 31 July. These will be verified by the AEC and the required material on the registered tickets will then be prepared and released as pdf documents on the AEC website on Sunday afternoon. I should be able to get them into the calculator software on Sunday and then some time on Monday we will publish all the ticket votes. The Senate Calculators should be available on Monday afternoon or some time on Tuesday.

Should swings be described as percentage or percentage points?

Either is correct. The argument comes about because a change in interest rates from 5% to 6% would always be described as a one percentage-point change. So using simlar terminology, if the Labor vote in a seat went from 50% to 53%, this would be a three percentage point swing. However, the number of voters shifting to creating this swing would also correspond to three percent of the electorate as a whole, so to say there has been a three percent swing is also valid because this is the percentage of the electorate to change.